This invention relates generally to power regulation circuits, and more particularly, it relates to a quad exchange power controller for use in network terminating equipment, private branch exchanges (PBX) or central office line cards. In one particular application, the power controller of the present invention is used to supply a regulated -40 volts up to four separate lines at a S interface.
In CCITT (Consultative Committee for Telegraphy and Telephony) terminology, the S or subscriber lines interface is used to interconnect terminal equipment in an Integrated Servies Digital Network (ISDN) to one end of the network terminating equipment. The other end of the network terminating equipment is typically joined to a transmission line or U interface, which connects to a line terminator or central office line card. The quad exchange power controller of the present invention consists of a microprocessor interface section for communication with a microprocessor and an analog section having four output drivers for driving independently the S interface lines. This quad exchange power controller is manufactured and sold by Advanced Micro Devices, Inc., Sunnyvale, Calif. under part No. Am7938. The power controller is an integrated circuit formed of a single-chip package and is used to individually control and monitor via a microprocessor each of the four lines at the S interface. Specifically, the power to each "S" line may be switched off when the temperature reaches 140.degree. C. and if the temperature continues to increase to 150.degree. C., then all of the four lines at the S interface are disabled. Further, the line-status or load conditions consisting of low-level voltage, open-loop current, current overload, reverse current and thermal overload on each S interface line is monitored by comparing line current and voltage with a reference level.